Download Marine Ecology Lecture, lecture 4

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• Since we know some of the habitats and
organisms that live in marine environments,
we can also study their interactions (w/ each
other and w/i the community structure)
• Ecology is the study of
the inter-relationships
between the physical
and biological aspects of
the environment.
• It is the study of how
organisms adapt to and
alter their environment.
Marine Ecology
• Ecology is the interaction between organisms
and their environment.
• These interactions affect the survival and
distribution of these organisms.
• Interactions can be very complex.
Ecosystem
All the biotic (living) and abiotic (nonliving)
components in a defined area.
• Ecosystems interact.
• All ecosystems require a constant input of
energy.
• Chemicals and nutrients are cycled within
ecosystems.
Population
A group of organisms of the same species occupying a specific
area
Community
All populations of organisms living in a defined area.
Habitat
The physical place where an organism lives.
Niche
The resources (biotic & abiotic) an organism uses for survival,
growth, and reproduction.
A Biological Community is “all of the populations of organisms living together (and
potentially interacting) within the ecosystem.”
Community Composition
• Physical factors (abiotic)
– temperature, salinity, dessication, pressure (etc.)
– can all limit where an organism can survive
• Biological factors (biotic)
– larval supply, competition, predation, parasitism
– can also limit where an organism can be found
• Some (physical, abiotic) environmental factors in
the marine environment we mentioned include:
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Temperature
Salinity
Pressure
Nutrients
Dissolved gases
Currents
Light
Suspended sediments
Substrate (bottom material)
River inflow (estuaries)
Tides
Waves
Physical Factors
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range of tolerance
Steno = narrow
Eury = wide or broad
Examples:
– stenothermal or eurythermal
– stenohaline or euryhaline
Needs of a Species
• Populations demand specific resources to
survive.
• These resources can affect population growth
if they are in short supply.
• These resources that have the ability to affect
the growth of a population are called limiting
resources.
• Thus your ABIOTIC FACTORS can be limiting!
Needs of a Species
• Even if an organism is able to acquire a
limiting resource, there is a maximum number
of organisms that any habitat can support.
• This number is known as the carrying capacity.
• As a population becomes more “crowded,” the
growth rate of that population will decrease.
Unrestrained
Growth:
unrealistic
because we
have
limiting
resources &
biotic factors
influencing
survival
Marine Ecology
Ways that Species can Interact
(i.e. the BIOTIC FACTORS):
1. Competition
2. Predator-Prey Interactions (a type of
competition)
3. Symbiosis
4. Larval Supply
Competition
• An organism can use a resource at the
expense of another organism.
• This may result in reduced ability of that
individual to reproduce or even survive.
• Poorer competitors may die out due to this
competition.
Competition
• Competition occurs when organisms must
“fight” with one another over a limiting
resource they both require for survival.
• Organisms can compete with members of
their own species – intraspecific competition –
or members of other species – interspecific
competition.
Competition
• limited supply of resources
• Intraspecific competition
– between individuals of the same species
– Leads to adaptation
• Interspecific competition
– between individuals of different species
– may lead to competitive exclusion
2 Hermit crabs fight (compete) over a snail shell – a new “home”
Competition
• Can lead to ADAPTATION by 1 organism or
many
• Can make organisms “adapt” their
behaviors (acting differently), “adapt”
physically (develop different physical
attributes to enhance their chances of
survival – large mouth/no teeth in a whale
shark)
Figure 10.6
• Interspecific Competition
Individuals of different species compete for
same resources (food, shelter, space).
What are possible outcomes of interspecific
competition?
• one individual excludes the other (principle
of competitive exclusion)
• they coexist (resource partitioning)
Interspecific Competition (Competitive
Exclusion):
• Balanus cannot withstand the currents,
temp. differential and dessication that
Chthamulus can thus Balanus “prefers” lower
limits.
• Balanus is larger and, during larval
recruitment, has a much better chance of
survival (& colonization) on rock
• ZONATION leads to Balanus outcompeting
Chthamulus in lower tidal ranges but
Chthamulus can still live in upper zone
Interspecific Competition (Competitive
Exclusion):
• Balanus upper and lower limit(s) thus set by
PHYSICAL factors
• Chathamulus lower limit thus set by
BIOLOGICAL factors (competition – for space
during larval recruitment) and upper limit
thus set by PHYSICAL factors (out of
intertidal zone = death)
Resource partitioning (interspecific
competition, part 2)Competing species can coexist if they use
the same resource in a slightly different
way or at a different time.
• Space on a rock (a habitat)
• Food (not enough of 1 kind for all)
The species must adapt to use a different
space or eat something different…but
TOGETHER.
It is a division of resources!
Resource Partitioning
Resource Partitioning
Symbiosis - one species living in or on another. The cooccurrence of two species in which the life of one is
closely tied with the life of another.
Types of Symbiosis:
1. Mutualism (++) both species benefit (example:
cleaning associations, clown fish, zooxanthelle,
cleaner shrimp).
2. Commensalism (+0) one species benefits with no
apparent effect on the other (example: barnacles
living on whales, pilotfish & shark).
3. Parasitism (+-) one species benefits & the other is
harmed (examples: tapeworms in the guts of whales,
roundworms).
More on Symbiosis
• If partners if a symbiotic relationship can live
without one another, this is known as
facultative symbiosis.
• If the partners cannot survive with the other
partner, this is known as obligate symbiosis.
• In all cases, the smaller partner is known as
the symbiont and the larger partner is called
the host.
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Figure 10.10
Figure 10.9
214037
Credit: © Carolina Biological/Visuals Unlimited
Nematode.
Elephantitis
from a
parasitic
nematode
Fig. 16.8e
Guinea worm (parasitic nematode)
removed
Predation
One species (predator) kills another (prey) for food.
• Can also affect community structure
• Allows for increased diversity when superior competitor is
preferred prey
Prey species often have adaptations that help them
avoid being eaten such as:
• Warning coloration (the opposite of camoflage!)
• Camouflage
• Mimicry
Flamboyant Cuttlefish
• Warning Coloration “warns” predators it’s poisonous!
Camouflage
Mimicry – top snake is venomous, a coral snake; bottom snake is not
(a red milk snake) but they share the same colors!
Larval Supply:
• Larval supply is a biotic factors influencing
community ecology but…
• Many factors effect larval survival (both
abiotic & biotic)
• Larval spawning typically occurs when food
resources are expected to be highest (biotic)
• Larval spawning typically occurs when
conditions are best (such as seasonal and
temperature conditions) (abiotic)
Larval Supply cont.:
• Remember: The BIOTIC FACTORS come “full
circle” here…competition (remember
competitive exclusion and zonation!) effects
where larvae can settle and (heavy) predation
can decrease larval supply before they even
get the chance!
• So…which comes 1st? The chicken or the egg?
Unrestrained
Growth:
unrealistic
because we
have
limiting
resources &
biotic factors
influencing
survival
Complete “Study” of Ecology is:
• Combination of “Environmental” Factors:
– biotic factors
– abiotic factors (+)
• Placing them (the organisms) in the
population/community (+)
• The specific habitat (where an organisms lives)
=
• NICHE!
1 example of a “habitat”
Study of Ecology
• Niche: an organism’s environmental role
– environmental factors
– biological factors
– the organism’s behavior